1. Field of the Invention
The present invention is related to an application of cell surface receptor that binds Mycobacterium tuberculosis, especially relating to an application of CD 13 receptor on inhibition of Mycobacterium tuberculosis infection of monocytes.
2. The Prior Arts
Tuberculosis (TB), with estimated annual death of two million cases, is a common deadly transmissible disease in developing countries. According to the World Health Organization's report, the average annual increase in tuberculosis is about 2% in recent years. The pathogen of TB is called Mycobacterium tuberculosis complex (MTBC), including Mycobacterium tuberculosis, M. bovis, M. africanum, M. microti, and M. canetti, in which Mycobacterium tuberculosis is the main pathogen of TB in human and the main infection site is lung.
It is estimated that one third of world populations (about 1.7 million/year) are infected with Mycobacterium tuberculosis. This is because virulence factor of Mycobacterium tuberculosis can enable the bacterium to avoid being killed by phagocytes and survive within host phagocytes. In the aspect of phagocyte detection of Mycobacterium tuberculosis, many receptors on the surface of Mycobacterium tuberculosis are important, indicating that receptors that facilitate mycobacterial entry into phagocytes have impact on survival opportunity of Mycobacterium tuberculosis. Mycobacterium tuberculosis binds to the cholesterol of phagocytes and lipid-rich region (also called lipid rafts) of host cell membrane, a site also having function of signal transduction. Inside host cells, Mycobacterium tuberculosis can degrade cholesterol as energy source during persistence of chronic infection. In addition, Mycobacterium tuberculosis will affect lipid transduction to block phagosome synthesis so as to protect itself from being transported to lysosome.
CD13 (aminopeptidase N) is a multi-functional protein present in many tissues that not only functions as an enzyme but reveals other functional activities through different mechanisms. CD 13 is found partly distributed in lipid rafts and affects cell membrane protein composition and cholesterol uptake. CD13 has been found in membrane-bound protein and in secretion of specific cells and degraded cell membrane in active form. For some specific virus, CD13 is a cell surface receptor, where virus can enter into cells by endocytosis.